Ball joint



FIG. 1 is a top perspective view of the ball joint;

FIG. 2 is a bottom perspective view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a rear elevation view thereof;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof;

FIG. 7 is a left side view thereof; and,

FIG. 8 is a right side view thereof.

The broken lines in the Figures are included for the purpose of illustrating environment and form no part of the claimed design. 

CLAIM The ornamental design for a ball joint, as shown and described. 